1. Field of the Invention
The present invention relates to a motorcycle in which a front end portion of a rear swing arm for rotatably supporting a rear wheel is swingably supported via a supporting shaft by an engine supported by a body frame, and particularly to an improved structure for supporting the rear swing arm to the engine.
2. Background Art
A motorcycle having a rear swing arm is known, for example, from Japanese Patent Laid-open No. Hei 10-115226. This motorcycle, however, has a shortcoming: because a pair of right and left rotatably supporting portions provided at a front end portion of a rear swing arm are swingably supported by both ends of a supporting shaft projecting from an engine, (both the rotatably supporting portions are supported in a cantilever manner only by the engine via the supporting shaft) the supporting shaft must be reinforced in order to reinforce the rigidity of the rear swing arm supported by the engine. This increases the weight of the motorcycle.
In light of this shortcoming, an object of the present invention is to provide a rear swing arm supporting structure for a motorcycle capable of enhancing the rigidity of a rear swing arm and having a reduced weight.
According to an embodiment of the invention, a rear swing arm supporting structure is provided in which a front end portion of a rear swing arm for rotatably supporting a rear wheel is swingably supported via a supporting shaft by an engine supported by a body frame. Upper end portions of a pair of right and left brackets are fixed to both ends of the supporting shaft supported by the engine, and a cross-member portion for connecting lower end portions of the brackets to each other is fixed to the engine at a position under the supporting shaft. A pair of right and left rotatably supporting portions provided at the front end portion of the rear swing arm are swingably supported by the supporting shaft at positions between the brackets and the engine.
In this embodiment, the right and left brackets are supported by the engine via the supporting shaft, and also supported by the engine via the cross-member portion for connecting both the brackets to each other. Both of the rotatably supporting portions provided at the front end portion of the rear swing arm are swingably supported between the engine and both the brackets forcibly supported by the engine at a plurality of positions. As a result, it is possible to enhance the rigidity of the rear swing arm supported by the engine while avoiding undue weight of the supporting shaft and the like.
The brackets have respective shaft holes in which both the ends of the supporting shaft passing through the engine with its relative axial position between the rotatably supporting portions fixed are to be inserted. One or two of the brackets have slit portions continuous to the inner surfaces of the shaft holes of the brackets, and fastening bolts for reducing the widths of the slit portions to reduce the diameters of the shaft holes. With this configuration, it is possible to easily position both the rotatably supporting portions along the axial line of the supporting shaft, irrespective of the accuracy of the gap between both side surfaces of a portion supporting the supporting shaft, of the engine and both the brackets, and the accuracy of the widths of both the rotatably supporting portions, and to easily fix the brackets to both the ends of the supporting shaft.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.